Telescoping gravity davit

ABSTRACT

A davit for use in lowering and raising life crafts such as life boats and survival capsules with respect to decking upon which the davit is supported. The davit comprises a fixed hollow beam which slidably receives a travelling boom which, in turn, houses a dump-hook assembly. The latter is capable of movement along the travelling boom. A cable extends from a power source through the davit and over the dump-hook to suspend the life craft beneath the davit. The fixed beam is canted so that its outboard end extends downwardly at an angle which permits outboard-directed movement, under the influence of gravity, of the travelling boom and dump-lock assembly once the holding brake or mechanism is released. Retraction of the dump-hook assembly and travelling boom into the fixed beam is provided by the powered cable. The outboard-directed movements of the travelling boom and dumphook assembly are coordinated so that termination of such movement of the travelling boom initiates the outboard-directed movement of the dump-hook assembly. The inboard-directed movements of these components are coordinated in a similar but in reverse manner. A cut-out is provided in the top of the outboard end of the travelling boom which cooperates with certain stops to limit the outboard movement of the dump-hook assembly and to cause it to rotate about a transverse axis to permit lowering of the life craft. The davit also includes components which ensure that the dump-hook assembly is retracted before the travelling boom commences to retract into the fixed beam.

United States Patent [191 Kariagin et al.

[451 Dec. 18, 1973 TELESCOPING GRAVITY DAVlT [75] Inventors: NikolaiKariagin, Chatsworth; Jerry Laibson; Eric Ralph Hooper, both of SanDiego; Jim Cowden Keogh, Jr., Cardiff; Augustine Joseph Ragan, El Cajon,all of Calif.

[73] Assignee: Whittaker Corporation, Los

Angeles, Calif.

[22] Filed: Dec. 15, 1972 [21] Appl. No.: 315,514

Primary ExaminerTrygve M. Blix Arsisrant Examiner-Donald W. UnderwoodAttorney-Donald E. Nist et a1.

[57] ABSTRACT A davit for use in lowering and raising life crafts suchas life boats and survival capsules with respect to decking upon whichthe davit is supported. The davit comprises a fixed hollow beam whichslidably receives a travelling boom which, in turn, houses a dump-hookassembly. The latter is capable of movement along the travelling boom. Acable extends from a power source through the davit and over thedump-hook to suspend the life craft beneath the davit. The fixed beam iscanted so that its outboard end extends downwardly at an angle whichpermits outboard-directed movement, under the influence of gravity, ofthe travelling boom and dump-lock assembly once the holding brake ormechanism is released. Retraction of the dump-hook assembly andtravelling boom into the fixed beam is provided by the powered cable.

The outboard-directed movements of the travelling boom and dump-hookassembly are coordinated so that termination of such movement of thetravelling boom initiates the outboard-directed movement of thedump-hook assembly. The inboard-directed movements of these componentsare coordinated in a similar but in reverse manner. A cut-out isprovided in the top of the outboard end of the travelling boom whichcooperates with certain stops to limit the outboard movement of thedump-hook assembly and to cause it to rotate about a transverse axis topermit lowering of the life craft. The davit also includes componentswhich ensure that the dump-hook assembly is retracted before thetravelling boom commences to retract into the fixed beam.

13 Claims, 10 Drawing Figures PATENTEB DEC 1 8 i913 SHEET 10? d SHEET? 2BF 4 PATENTED DEC 1 8 i875 PATENIED DEC 18 1925 SHEET 3 OF 4lllllllllllllllll l p hnh Pmmmumams I 3,778,855

. saw no? 4 BACKGROUND OF THE INVENTION This invention relates to lifecraft handling and, more particularly, to a canted telescoping davitwhich is extensible by gravity.

Davits have long been in use on ships and artificial islands, e.g.,off-shore oil drilling rigs, as evidenced by U.S. Pat. No. 646,181issued Mar. 27, 1900. Although most of the davits, until recently, havebeen mechanical davits which employ a power source to produce outboard(as well as inboard) movement of the life craft, the current trend istoward employment of gravity davits, particularly for larger lifecrafts, which are canted to use gravity to produce outboard movement ofthe life craft. Inboard movement of a life craft on a gravity davit issimilar to that on a mechanical davit.

The reason for the present preference for gravity davits over mechanicaldavits is that functioning of the gravity davits, especially when a lifecraft is to be lowered into water, is much more predictable andreliable.

Gravity davits have been patented as evidenced by U.S. Pat. Nos.2,929,081 and 2,949,617, issued on Mar. 22, 1960 and Aug. 28, 1960 toH.G. Taylor. A disadvantage of the gravity davit described in thesepatents is that the life craft remains suspended at the outboard end ofthe travelling davit arm rather than being drawn inboard along at leasta portion of the latters length. This means that the life craft is notdrawn inboard as far as it can be for more compact storage and tominimize torque loading resulting from suspension of the life craft. Italso means that maximum torque loading is always applied to thetravelling davit arm which thereby subjects the latter and thestationary tracks to substantial bending stresses.

SUMMARY OF THE INVENTION This invention is embodied in a telescopinggravity davit which comprises a hollow beam which is canted downward inan outboard direction and which is mounted in a fixed position above adeck with respect to which a life craft is to be lowered or raised. Thefixed beam slidably receives a travelling boom which, in turn, houses adump-book assembly which has limited travel within the travelling boom.A cable extends from a power source through the davit and over thedumphook for connection to a life craft which is stored immediatelyunder the fixed beam.

An actuator is provided on the travelling boom which is connected to aretaining mechanism mounted in the travelling boom which normallyrestrains the dumphook assembly from movement relative to the travellingboom. The actuator cooperates with a stop mounted within the fixed beamto initiate outboard movement of the dump-hook assembly simultaneouslywith termination ofthe outboard movement of the travelling boom. It alsocooperates with this stop to lock the dump-hook assembly into theretaining mechanism at the end of the inboard movement of the dump-hookassembly at the same time as the travelling boom commences its inboardmovement.

A cut-out is also provided in the outboard end of the travelling boom tocooperate with stops located in that end of the boom to both terminatethe outboard movement of the dump-hook assembly and to cause it torotate about a transverse axis to release the life craft for descentinto the water.

A major advantage of the herein-described structure is that it occupiesa minimum of space since the dumphook assembly, below which the lifecraft is suspended, retracts into the fixed beam. Additionally, the lifecraft in its stored position is located relatively close to the inboardend of the fixed beam to minimize severe loads during storage in severeenvironments.

DESCRIPTOIN OF THE DRAWINGS FIG. 1 is a side elevation view of theherein-described gravity davit supported above a deck and supporting asurvival capsule;

FIG. 2 is a side elevational view of the gravity davit of FIG. 1 showingit in its stowed condition.

FIG. 3 is a side elevational view of the gravity davit of FIG. 1 showingthe travelling boom in its outboard position.

FIG. 4 is a top plan view of the gravity davit of FIG. 1 showing thedump-hook assembly and travelling boom in their outboard positions.

FIG. 5 is an end elevational view of the gravity davit taken along theline 5-5 of FIG. 2.

FIG. 6 is a cross-sectional view of the fixed beam taken along the line66 of FIG. 3.

FIG. 7 is a cross-sectional view of the dump-hook assembly taken alongthe line 7-7 of FIG. 3.

FIG. 8 is a sectional view of the travelling boom showing the dump-hookassembly in side elevation in its inboard position.

FIG. 9 is a sectional view of the travelling boom showing the dump-hookassembly in side elevation in its outboard position and rotated torelease a capsule.

FIG. 10 is a perspective view of a valley stop.

DESCRIPTION OF THE PREFERRED EMBODIMENT As shown in FIG. 1, the numeral10 designates the hereindescribed gravity davit which is shown supportedabove a deck, platform or superstructure l2 (generically referred toherein as a deck" or decking) by suitable support means such as thesupport bars 14. Other types of support means may be employed as is wellknown and they will not be further described as the particular design ofthe support means does not constitute a part of this invention. Thesupport bars 14 cant or angle the gravity davit 10 with respect to thedeck 12 so that it can be extended by gravity as will be described inmore detail hereafter. This canting of the gravity davit 10 provides itwith a downwardlyextending, outboard end and with an upwardlyextendinginboard end.

In FIG. 1, a survival capsule 20 such as is described in U.S. Pat. No.3,259,926, issued July 12, 1966, is shown suspended from the gravitydavit 10 in its inboard (solid outline) and outboard (phantom line)positions. The survival capsule 20 is shown for exemplary purposes only,as it will be appreciated that other life crafts and even bodies notused for life-saving purposes may be suspended from the gravity davit10.

The gravity davit 10 comprises a fixed hollow beam 22 to which thesupport rods 14 are connected, a hol- 1 low travelling boom 24 whichtelescopes into and is slidable within the fixed beam 22, a dump-hookassembly 26 which is carried within the travelling boom 24 for slidablemovement within the latter, and cable and powered winch means forcontrolling the rate of outboard movement of the capsule 20 and forreturning the capsule to its inboard position. Both the travelling boom24 and dump-hook assembly 26 have inboard and outboard positions withmovement of each between their respective inboard and outboard positionstaking place while the other is at rest. In FIG. 2, the travelling boom24 is shown in its inboard position retracted into the fixed beam 22with the dump-hook assembly 26 located at its inboard position withinthe travelling boom 24 directly above the capsule 20. Under theinfluence of gravity, the travelling boom 24 moves to its outboardposition which is shown in phantom outline in FIG. 1 and in solid linein FIG. 3. Also under the influence of gravity, the dump-hook assembly26 moves to its outboard position within the travelling boom 24 (FIG.4).

Outboard movement of the capsule 20 is gravityinduced with its ratebeing controlled both by the angle (with respect to the horizontal) ofthe davit l and by brake means, whereas inboard movement of the capsule20 is governed by separate power means. The latter, as shown in FIG. 1,comprises a motor 28 which may be mounted on the davit (as shown in FIG.I) or on the deck 12 and which is operably connected to a winch 30. Abrake 31 such as that disclosed in U. S. Pat. No. 3,702,690, issued Nov.14, I972, may be employed as the brake means to govern the rate ofrotation of the winch 30. A cable 32 is attached at one end to the winch30 and extends through the davit 10 for attachment at its other end tothe capsule 20. As the capsule 10 moves outboard under the influence ofgravity, a restraining force is applied to it throughthe cable 32 by thebrake 31 acting on the winch 30. To return the capsule to its inboardposition, the rotation of the winch 30 is reversed and the motor 28controls its rotation so that the cable 32 is taken up to thereby returnthe dump-hook assembly 26 and travelling boom 24 to their respectiveinboard positions as will be described in more detail hereinafter.

The fixed beam 22 will next be described with particular reference toFIGS. 2-6. This beam 22 is internally provided with an overhead V-rail34 and an inverted-V, surface rail 36 between and along which thetravelling boom 24 runs. The overhead rail 34 depends from the ceiling38 of the fixed beam 22 and extends more than half-way to the lattersoutboard end 40 from adjacent its inboard end 42 preferablysymmetrically disposed along the vertical, longitudinal center line ofthe fixed beam 22. The surface rail 36 extends upwardly from the floor44 of the fixed beam 22 and is also preferably symmetrically disposedalong the vertical center-line of the latter so that it is substantiallydiametrically opposed to the overhead rail 34. Additionally, the surfacerail 36 is substantially co-extensive with the overhead rail 34 exceptthat the surface rail terminates a spaced distance from the inboard end42 of the fixed beam 22. Between the inboard end of the surface rail 36and that of the fixed beam 22, the floor 44 of the fixed beam defines acentrally-disposed slot 46 (FIG. 4 and 6). Bearing means 48 are carriedwithin the fixed beam 22 by upturned flanges 50 disposed adjacent thisslot 46 so that a sheave 52 which is rotatably supported on the bearingmeans partially extends through the slot.

Adjacent the outboard end 40 of the fixed beam 22, a pair of rollerbearings 54 (FIG. 5) are rotatably mounted in the side walls 56 of thefixed beam to support a pair of rollers 58,60, thereon within the fixedbeam. Preferably, the rollers 58,60 include a V-type roller 58 and aflat roller 60 having side shoulder recesses 61.. An elongated slot 62is formed in the floor 44 of the fixed beam 22 and extends inboard fromthe outboard end 40 thereof to terminate short of the surface rail 36 topermit extension of the cable 32 and a portion of the dump-hook assembly26 downwardly therethrough from the inboard position of the dump-hookassembly 26 to the outboard end of the fixed beam 22 so that the capsule20 remains disposed vertically below the dump-hook assembly 26 at alltimes.

Still referring to FIG. 2-6, the travelling boom 24 is essentiallyhollow with its sides defining a pair of opposing, inwardly-facing,guide channels 64 which cooperate to guide the dump-hook assembly 26along the travelling boom 24. The bottom wall of the travelling boom 24is provided with a longitudinal slot 65 (FIG. 4) extending from theoutboard end 78 of the travelling boom to the inboard position of thedump-hook assembly 26 to permit extension therethrough of the cable 32and part of the dump-hook assembly.

Means are provided on the travelling boom 24 for rolling engagement withthe overhead and surface rails 34, 36 within the fixed beam 22. Suchmeans includes a pair of V-pulleys 66,68 which are rotatably mounted onbrackets 70, 72 affixed to the inboard end 74 and to the undersideadjacent to the inboard end 74, respectively, of the travelling boom 24to engage the overhead and surface rails 34,36, respectively, of thefixed beam 22. The travelling boom 24 is also provided with a V-typeguide rail 76 depending from the underside of the travelling boom 24 forengagement with the V-roller 58 carried adjacent the outboard end 40 ofthe fixed beam 22. The guide rail 76 extends from the outboard end 78 ofthe travelling boom 24 inwardly a distance sufficient to provideengagement of this guide rail 76 with the V-roller 58 over the length oftravel of the travelling boom 24. The opposite side of the underside ofthe travelling boom 24 is provided with a flat surface 79 for rollingengagement with the flat roller 60 which is mounted along side theV-roller 58. The flat surface 79 is substantially co-extensive with theguide rail 76.

In summary, the travelling boom 24 is capable of inboard and outboardmovement within the fixed beam 22. When so moving, the travelling boom24 is supported by the V- and flat rollers 58,60 mounted adjacent theoutboard end 40 of the fixed beam and by the pulley 68 mountedunderneath the travelling boom 24 adjacent its inboard end 74. As thetravelling boom 24 moves towards its outboard position (FIG. 3), itsinboard end section exerts an increasing force upwardly against theceiling 38 of the fixed beam 22. Friction produced by this force isminimized due to the rolling action of the pulley 66 as it moves alongthe overhead rail 34 depending from the fixed beam ceiling 38.

Inboard movement of the travelling boom 24 preferably stops when it issubstantially telescoped into the fixed beam 22 to provide the mostcompact package to thereby minimize the space occupied by the gravitydavit 10 when not in use. Such inboard movement of the travelling boom24 may be controlled by contact of the latter with a limit switch (notshown) which functions to cut off power to the winch 30. A dead-manbrake (not shown) is applied at this point to prevent rotationalmovement of the winch 30 and, thus, outboard movement of the travellingboom 24 until the deadman brake is released.

Outboard movement of the travelling boom 24 is also limited. A stopblock 82 is attached to the topside surface of the travelling boom 24 aspaced distance from its inboard end 74 so that the travelling boom 24reaches its outboard position (FIG. 3), the stop block 82 abuts againstanother stop block 84 which depends from the ceiling 38 of the fixedbeam 22. Additionally, a pair of valley stops 85 are positioned in thebottom of the travelling boom 24 adjacent to the inboard ends of each ofthe flat surface 80 and guide rail 76 on the underside of the travellingboom. The valley stops 85 may be constructed as shown in FIG. and allvalley stops may or may not be the same. Referring to FIG. 10, thevalley stop 85 comprises a block 86 which has a face 87 which islaterally defined by walls 88 which project from the block. Transverse,aligned grooves 89,91 are formed in the walls 88 and block surface 87,respectively, to receive the V- and flat rollers, 58,60. When thetravelling boom 24 travels outward, the flat and V-rollers 60,58, ineffect, travel to the inboard ends of the flat surface 80 and guide rail76, respectively, where they then drop into the valley stops 85 wherethey remain until the travelling boom 24 is retracted into the fixedbeam 22.

Turning now to the dump-hook assembly 26, the latter is shown in itsinboard positions (with respect to the travelling boom 24) in both FIG.2 and 3 and in its outboard position in FIG. 4. With particularreference to FIG. 7-9, the dump-hook assembly 26 comprises a pair ofhook plates 90 which, in turn, comprise upper and lower jaw sections92,94, respectively, defining a mouth 95. The hook plates 90 are spacedapart from each other by spacers 96 welded thereto. Each upper jawsection 92 has a normally inboard extension 98 to which a pin 100 iswelded for rotatably mounting a roller 102 external to the hook plates90 so that they are spaced apart and sized to be received by the guidechannels 64 formed internally of the travelling boom 24. A sheave 104 isrotatably mounted between the hook plates 90 out-board of the rollers102 on the upper jaw section 92 on a pin 106 extending between andthrough the hook plates. The cable 32 extends over the sheave 104. Asecond pair of rollers 107 are rotatably carried on the pin 106 externalto the hook plates 90 for reception by the travelling boom opposingguide channels 64. Normally, the extension 98 of the upper jaw section92 is tilted inboard with respect to that portion of the upper jawsection which carries the sheave 104 so that the mouth 95 is tilted withits open end up.

The dump-hook assembly 26 is maintained in its inboard position by alatch mechanism 108 (FIG. 2-4 and 8) which is hydraulically operated.The latch mechanism 108 comprises a bell crank 110 which is pivotallymounted at its apex to a supporting bracket 112 by a pivot pin 114extending therethrough. The supporting bracket 112, in turn, is affixedto a base plate 116 on the bottom of, and within, the travelling boom24. An inboard arm 117 of the bell crank 110 is pivotally connected to apiston 118 which extends into one end ofa hydraulic cylinder 120 whichis anchored at its other end to the base plate 116 and which is operablyconnected through hydraulic fluid lines 122, 123 to a contact-actuated,valve release trigger 124 (FIG. 2 and 3) mounted on the underside of thetravelling boom 24. The outboard arm 126 of the bell crank 110 has agroove 128 formed in its inner side to receive a locking pin 130extending between, and connected to, the hook plates 90.

When the dump-hook assembly 26 is in its inboard position with respectto the travelling boom 24, an hydraulic valve is closed so that thepiston 118 is in its retracted position in the hydraulic cylinder 120.This forces the bell crank to pivot about the base pivot pin 114 so thatthe outboard arm 126 is elevated as shown in solid line in FIG. 8 tothereby retain the locking pins in the groove 128 in the outboard arm sothat the dump-hook assembly 26 is prevented from moving outboard fromits inboard position.

As the travelling boom 24 travels in an outboard direction from itsinboard position, as previously described, the dump-hook assembly 26 iscarried therein in its inboard position. When the travelling boom 24 hasreached its outboard position, the dump-hook assembly 26 is thenreleased for its outboard travel. At the same time that the stops 84,82on the fixed beam 22 and travelling boom 24, respectively, abut oneanother to stop the outboard movement of the travelling boom and the V-and flat rollers 58,60 drop into the valley stops 85, the valve releasetrigger 124 is depressed by contact with a stop extending upwardly fromthe floor 44 of the fixed beam 22. Such contact allows release ofhydraulic fluid from the cylinder 120 through line 123 so that thedownward load acting through the bell crank 110 on the piston 118 willextend the piston 118 to permit counterclockwise pivotal movement (asseen in FIG. 8) of the bell crank 110 about its base pivot pin 114 to,in turn, permit the outboard arm 126 of the bell crank to tiltdownwardly (as shown in dashed outline in FIG. 8) so that the lockingpin 130 is pulled out of its retaining groove 128 by the weight of thedump-hook assembly 26 acting under the influence of gravity. The bellcrank 110 immediately returns under the influence of an internalcylinder spring (not shown). The dump-hook assembly 26 is then free tomove toward its outboard position under the continuing influence ofgravity, but subject to restraint by a governor brake acting against thewinch 30 with the restraining force being transmitted to the dump-hookassembly 26 through the cable 32.

Outboard movement of the dump-hook assembly 26 is limited by abutment ofthe outboard rollers 107 against stop blocks 142 attached to the innersides of the travelling boom 24. At the same time, the outboard rollers107 of the dump-hook assembly 26 drop into valley stops 144 (FIG. 2 and3) similar to those designated by the numeral 85 so that the dump-hookassembly cannot prematurely return.

To permit the capsule 20 to be lowered, the dumphook assembly 26 ispermitted to rotate about the axis of the sheave 104 until the mouth 95of the dump-hook assembly is tilted downward to permit release of abobbin-like fitting 146 swaged to the cable 32 from the jaws 92,94 ofthe dump-hook assembly 26. This is shown by a comparison of FIG. 8 and9. This is accomplished by providing a cut-out 148 in the top of thetravelling boom 24 so that the inboard extension 98 of the upper jawsection 92 together with the rollers 102 carried thereon are free torotate upwardly through the cut-out 148 about the sheave 104 axis whenthe outboard rollers 107 drop into the valley stops 104. This rotationalmovement of the inboard extension 98 is limited by its abutment with alimit pin 150 affixed to the travelling boom 24 outboard of the cut-out148. Abutment of the inboard extension 98 with the rotational limit pin150 occurs after the jaws 92,94 have been sufficiently tilted to permitescape of the cable fitting 146 from the mouth 95 of the dump-hookassembly 26. As the dump-hook assembly 26 rotates, the cable 32 is able,in effect, to pass between the hook plates 90 and the rollers 102because the pins 100 on which the rollers 102 are mounted do notinterconnect the hook plates so that a passageway is left therebetweenin the region of the inboard extension 98.

To retrieve and stow the capsule 20, the winch 30 is reversed as poweris applied thereto by the motor 28 to wind in the cable 32. As thecapsule is raised, the cable fitting 146 comes in contact with the loweredge of tee upper jaw section 92 of the dump-hook assembly 26. The cablefitting 146 is urged into the mouth 95 of the dump-hook assembly 26which simultaneously commences to rotate clockwise (as viewed in FIG. 9)about the sheave 104 axis. Movement of the cable fitting 146 into themouth 95 and rotation of the dumphook assembly 26 are both facilitatedby the eccentric position of the cable fitting with respect to the axisof rotation through the sheave 104 which thereby produces a torque onthe dump-hook assembly 26 causing it to rotate clockwise (as viewed inH0. 9) and by the curvature given to the lower edge of the upper jawsection 92. Rotation of the dump-hook assembly 26 continues until theinboard rollers 102 are returned to the guide channels 64 in thetravelling boom 24. Then, and not before, the force transmitted throughthe cable 32 from the motor 28 to the dump-hook assembly 26 issufficient (in the absence of dump-hook assembly rotation) to pull thelatter out of its valley stops 144 to start it on its inboard journeyalong the travelling boom 24.

As the dump-hook assembly 26 approaches its inboard position, thelocking pin 130 depresses the outboard arm 126 of the bell crank 110 tobe received by the groove 128. Substantially simultaneously therewith,the inboard rollers 102 contact another pair of stops 152 attached tothe inner sides of the travelling boom 24 causing the latter to beginits inboard journey into the fixed beam 22 as force continues to beexerted on the dump-hook assembly 26 through the cable 32. As thetravelling boom 24 begins its inboard journey, the valve release trigger124 moves inboard out of contact with the fixed beam stop 140. Thiscauses the piston 118 to be retracted into the hydraulic cylinder 120which causes pivotal movement of the bell crank 110 to retain thelocking pin 130 in the bell crank groove 128.

As the dump-hook assembly 26 reaches its maximum inboard position withinthe travelling boom 24, it causes the travelling boom 24 to move inboardlifting the travelling boom valley stops from the fixed beam rollers58,60 and the travelling boom telescopes into the fixed beam 22 untilit, too, reaches its inboard position at which time power to the winch30 is cut off as previously described. Conventional brake systems may beemployed to ensure that the gravity davit 10 remains stowed.

We claim:

1. A telescoping gravity davit, comprising a hollow fixed beam havingfirst and second ends and defining an elongated slot extending from saidfirst end toward said second end in the bottom thereof;

a hollow travelling boom slidably receivable by said fixed beam andhaving first and second ends and defining an elongated slot extendingfrom said first ends towards said second end in the bottom thereof injuxtaposed, aligned relation with said slot in said fixed beam;

first limit means attached to said fixed beam and to said travellingboom for limiting further movement of said travelling boom relative tosaid fixed beam after said travelling boom has been substantiallyextended from said fixed beam;

a dump-hook assembly slidably carried within said travelling boom fortravel therealong towards said first end of said travelling boom from astowed position within said travelling boom for suspending a bodytherebelow from a cable extending through said aligned slots and oversaid dump-hook assemy;

releasable locking means positioned within said travelling boomintermediate the ends thereof for locking said dump-hook assembly insaid stowed position intermediate said ends of said travelling boom andfor releasing said assembly in an outboard direction;

actuation means connected to said locking means and positioned on saidfixed beam and said travelling boom to (l) actuate said locking means torelease said dump-hook assembly therefrom for movement toward said firstend of said travelling boom at substantially the same time as said firstlimit means acts to stop movement of said travelling boom outward ofsaid fixed beam and to (2) actuate said locking means to lock saiddump-hook assembly in said stowed position at substantially the sametime as said dump-hook assembly returns to said stowed position; and

second limit means positioned on said travelling boom adjacent its firstend for engagement with said dumphook assembly to limit movement of saiddump-hook assembly toward said first end of said travelling boom.

2. The davit of claim 1 including:

stop means positioned within said travelling boom for engagement withsaid dump-hook assembly at substantially the same time as said dump-hookassembly re-engages said locking means to permit commencement ofmovement of said travelling boom into said fixed beam at substantiallythe same time as said dump-hook assembly returns to said stowedposition.

3. The davit of claim 1, further including rotation means carried onsaid trvelling boom adjacent said first end thereof for rotating saiddumphook assembly to release said body therefrom when said dump-hookassembly engages said second limit means.

4. The davit of claim 1 wherein said actuation means comprises:

contact means positioned within said fixed beam; and

trigger means operably connected to said locking means and carried onsaid travelling boom in a position such that l said trigger meanscontacts said contact means on said fixed beam at substantially the sametime as said first limit means acts to stop movement of said travellingboom outward of said fixed beam and (2) said trigger means moves out ofcontact with said contact means at substantially the same time as saiddump-hook assembly reengages said locking means.

5. A telescoping gravity davit, comprising: a hollow fixed beam having afirst and a second end and defining an elongated slot extending fromsaid first end toward said second end in the bottom thereof;

a hollow travelling boom slidably receivable by said fixed beam andhaving first and second ends and defining an elongated slot extendingfrom said first end toward said second end in the. bottom thereof injuxtaposed alignment with said slot in said fixed beam;

first stop means attached to said fixed beam intermediate the endsthereof;

second stop means attached to said travelling boom intermediate the endsthereof for engagement with said first stop means to limit movement ofsaid travelling boom out of said fixed beam after said travelling boomhas been substan-tially extended from said fixed beam;

a dump-hook assembly slidably carried within said travelling boom fortravel therealong towards said first end of said travelling boom from astowed position intermediate said ends of said travelling boom, saiddump-hook assembly suspending a body therebelow on a cable extendingthrough said aligned slots and over said dump-hook assembly;

releasable locking means positioned within said travelling boom forlocking said dump-hook assembly in said stowed position;

contact means positioned within said fixed beam;

trigger means operably connected to said locking means to actuate saidlocking means to alternately release and lock said dump-hook assemblyfrom and into, respectively, said locking means, and psitioned on saidtravelling boom 1) so that it contacts said contact means on said fixedbeam at substantially the same time as said second stop means on saidtravelling boom engages said first stop means on said fixed beam torelease said dump-hook assembly for movement along said travelling boomtoward said first end thereof at substantially the same time as saidtravelling boom stops its outward travel relative to said fixed beam and(2) so that it moves out of contact with said contact means atsubstantially the same time as said dump-hook assembly re-engages saidlocking means to lock said dump-hook assembly in said stowed position;

third stop means positioned within said travelling boom for engagementwith said dump-hook assembly when said dump-hook assembly re-engagessaid locking means; and

fourth stop means positioned within said travelling boom adjacent itsfirst end to limit movement of said dump-hook assembly toward said firstend.

6. The davit of claim 5 wherein:

said travelling boom defines a pair of inwardlysaid dump-hook assemblyincludes first and second roller means receivable by said travellingboom guide channels for guiding said dump-hook assembly therealong, saidfirst roller means being positioned closest to said first end of saidtravelling boom and said second roller means being spaced therefrom sothat said second roller means rotates out of said guide channels throughsaid cut-out when said dump-hook assembly engages said fourth stop meansand rotates about a transverse axis through said first roller meansunder the influence of the weight of said body.

7. The davit of claim 6 which further includes:

first valley stop means disposed within said travelling boom adjacentsaid first end and sized to partially receive said first roller means ofsaid dump-hook assembly substantially at the same time as said dump-hookassembly engages said fourth stop means adjacent said first end of saidtravelling boom.

8. The davit of claim 7 which further includes:

third roller means rotatable carried within said fixed beam adjacent anend thereof through which said travelling boom projects; and

second valley stop means disposed under said travelling boomintermediate said first and second ends to partially receive said thirdroller means, said second valley stop means being positioned so thatsaid second valley stop means receives said third roller means atsubstantially the same time as said trigger means contacts said contactmeans and said first and second stop means abut each other.

9. The davit of claim 6 wherein said dump-hook assembly furtherincludes:

a pair of spaced plates defining a pair of aligned, generally horizontalslots which form a mouth opening toward said first end of saidtravelling boom, said first and said second roller means being rotatablymounted on outwardly-facing sides of said spaced plates; and

a sheave rotatably carried by and between said first and second platesbetween said first roller means.

10. The gravity davit of claim 5 which further includes:

means for supporting said gravity davit above a deck at an anglerelative thereto with said first end of said fixed beam projectingdownwardly so that said travelling boom and said dump-hook assembly arefree to roll along said fixed beam and said travelling boom,respectively, under the influence of gravity;

said cable extending through said fixed beam and said travelling boomand over said dump-hook assembly to attach at one end to said bodysuspended below said dump-hook assembly and at its other end to a winch;

brake means associated with said winch for controlling the rate ofgravitationally-induced movement of said travelling boom and saiddump-hook assembly; and

power means connected to said winch for retracting said travelling boominto said fixed beam and for returning said dump-hook assembly to saidstowed position.

11. A telescoping gravity davit comprising:

a hollow fixed beam having an inboard and an outboard end and definingan axially-aligned, elongated slot extending from said outboard end asubstantial distance toward said inboard end along the bottom of saidfixed beam;

a hollow, travelling boom sized to telescope into said fixed beam andhaving an inboard end and an outboard end and defining anaxially-aligned, elongated slot in its bottom wall vertically spacedabove said elongated slot in said fixed beam and extending from saidoutboard end a substantial distance toward said inboard end, saidtravelling boom further defining a pair of inwardly-facing, opposingguide channels extending from said outboard end a substantial distancetoward said inboard end, said guide channels communicating with theexterior of said travelling boom through a cut-out in the top thereofadjacent said outboard end;

first movement means carried on said travelling boom;

second movement means disposed within saidfixed beam for cooperationwith said first movement means to provide rolling movement of saidtravelling boom with respect to said fixed beam when said fixed beam istilted with respect to the horizontal;

first stop means disposed within said fixed beam;

second stop means carried on said travelling boom for engagement withsaid first stop means to limit outboard-directed movement of saidtravelling boom relative to said fixed beam;

a dump-hook assembly disposed within said travelling boom'for movementrelative thereto between an outboard position adjacent said outboard endof said travelling boom and an inboard position intermediate said endsof said travelling boom, said elongated slots and said opposing guidechannels extending inboard to said inboard position of said dump-hookassembly when said travelling boom is substantially telescoped into saidfixed beam, said dump-hook assembly comprising,

a pair of vertically-aligned, spaced plates defining a pair of aligned,generally horizontal slots forming a mouth opening toward said outboardend of said travelling boom,

first and second roller means rotatably mounted on outwardly-facingsides of said spaced plates and sized to be received by said guidechannels in said travelling boom for guiding said dump-hook assemblytherealong, said first roller means being positioned closest to saidoutboard end of said travelling boom and said second roller means beingspaced therefrom so that said second roller means rotates out of saidguide channels through said cut-out when said dump-hook assembly isrotated about a transverse axis through said first roller means, and

a sheave rotatably carried between said plates between said first rollermeans for guiding a cable thereover;

locking means disposed within said travelling boom for locking saiddump-hook assembly in said inboard position;

contact means positioned within said fixed beam;

trigger means operably connected to said locking meand and positioned onsaid travelling boom (1) so that it contacts said contact means on saidfixed beam at substantially the same time as said second stop means onsaid travelling boom engages said first stop means on said fixed beam torelease said dump-hook assembly from said locking means for 6 travelrelative to said fixed beam and (2) so that it moves out of contact withsaid contact means at substantially the same time as said dump-hookassembly re-engages said locking means;

third stop means positioned within said travelling boom for engagementwith said dump-hook assembly when said dump-hook assembly re-engagessaid locking means at its inboard position to limit inboard-directedmovement of said dump-hook as sembly;

fourth stop means carried within said travelling boom adjacent its saidoutboard end for limiting outboard-directed movement of said dump-hookassembly, said fourth stop means being positioned outboard of saidcut-out a spaced dis-tance to permit rotation of said second rollermeans out of said guide channels when said outboard-directed movement ofsaid dump-hook assembly stops;

first valley stop means positioned within said guide channels of saidtravelling boom adjacent its outboard end and sized to partially receivesaid first roller means at substantially the same time as said dump-hookassembly con-tacts said fourth stop means;

second valley stop means carried on the underside of said travellingboom and engageable with said second movement means at substantially thesame time as said first and second stop means engage each other.

12. The gravity davit of claim 11 wherein:

said first movement means comprises,

a first pulley carried on and extending above said travelling boomadjacent its inboard end,

a second pulley attached to and depending from said travelling boomadjacent its inboard end, and

track means on the undersurface of said travel-ling boom extending fromadjacent its outboard end towards its inboard end; and

said second movement means comprises,

a first rail attachment to and depending from the roof of said fixedbeam and extending from adjacent its inboard end towards its outboardend for engagement with said first pulley,

a second rail attached to and extending upwardly from the floor of saidfixed beam and extending from adjacent its inboard end towards itsoutboard end for engagement with said second pulley, and

roller means disposed within said fixed beam adjacent its outboard endand extending upwardly from said floor of said fixed beam for engagementwith said track means on said travelling boom, said roller means beingpartially receivable by said second valley stop means.

13. The gravity davit of claim 11 which further includes:

means for supporting said gravity davit above a deck at an anglerelative thereto with said outboard end of said travelling boomprojecting downwardly so that said travelling boom and said dump-hookassembly are free to roll along said fixed beam and said travellingboom, respectively, under the influence of gravity;

said cable extending through said fixed beam and said travelling boomand over said dump-hook assembly sheave to attach at one end to a bodysus- 3,778,855 13 14 pended below said dump-hook assembly and at itsbly; and other end to a winch; power means connected to said winch fordrawing brake means associated with said winch for controlsaidtravelling boom and said dump-hook assembly ling the rate ofoutboard-directed movement of inboard. said travelling boom and saiddump-hook assem-

1. A telescoping gravity davit, comprising a hollow fixed beam havingfirst and second ends and defining an elongated slot extending from saidfirst end toward said second end in the bottom thereof; a hollowtravelling boom slidably receivable by said fixed beam and having firstand second ends and defining an elongated slot extending from said firstends towards said second end in the bottom thereof in juxtaposed,aligned relation with said slot in said fixed beam; first limit meansattached to said fixed beam and to said travelling boom for limitingfurther movement of said travelling boom relative to said fixed beamafter said travelling boom has been substantially extended from saidfixed beam; a dump-hook assembly slidably carried within said travellingboom for travel therealong towards said first end of said travellingboom from a stowed position within said travelling boom for suspending abody therebelow from a cable extending through said aligned slots andover said dump-hook assembly; releasable locking means positioned withinsaid travelling boom intermediate the ends thereof for locking saiddump-hook assembly in said stowed position intermediate said ends ofsaid travelling boom and for releasing said assembly in an outboarddirection; actuation means connected to said locking means andpositioned on said fixed beam and said travelling boom to (1) actuatesaid locking means to release said dump-hook assembly therefrom formovement toward said first end of said travelling boom at substantiallythe same time as said first limit means acts to stop movement of saidtravelling boom outward of said fixed beam and to (2) actuate saidlocking means to lock said dumphook assembly in said stowed position atsubstantially the same time as said dump-hook assembly returns to saidstowed position; and second limit means positioned on said travellingboom adjacent its first end for engagement with said dumphook assemblyto limit mOvement of said dump-hook assembly toward said first end ofsaid travelling boom.
 2. The davit of claim 1 including: stop meanspositioned within said travelling boom for engagement with saiddump-hook assembly at substantially the same time as said dump-hookassembly re-engages said locking means to permit commencement ofmovement of said travelling boom into said fixed beam at substantiallythe same time as said dump-hook assembly returns to said stowedposition.
 3. The davit of claim 1, further including rotation meanscarried on said trvelling boom adjacent said first end thereof forrotating said dump-hook assembly to release said body therefrom whensaid dump-hook assembly engages said second limit means.
 4. The davit ofclaim 1 wherein said actuation means comprises: contact means positionedwithin said fixed beam; and trigger means operably connected to saidlocking means and carried on said travelling boom in a position suchthat (1) said trigger means contacts said contact means on said fixedbeam at substantially the same time as said first limit means acts tostop movement of said travelling boom outward of said fixed beam and (2)said trigger means moves out of contact with said contact means atsubstantially the same time as said dump-hook assembly re-engages saidlocking means.
 5. A telescoping gravity davit, comprising: a hollowfixed beam having a first and a second end and defining an elongatedslot extending from said first end toward said second end in the bottomthereof; a hollow travelling boom slidably receivable by said fixed beamand having first and second ends and defining an elongated slotextending from said first end toward said second end in the bottomthereof in juxtaposed alignment with said slot in said fixed beam; firststop means attached to said fixed beam intermediate the ends thereof;second stop means attached to said travelling boom intermediate the endsthereof for engagement with said first stop means to limit movement ofsaid travelling boom out of said fixed beam after said travelling boomhas been substan-tially extended from said fixed beam; a dump-hookassembly slidably carried within said travelling boom for traveltherealong towards said first end of said travelling boom from a stowedposition intermediate said ends of said travelling boom, said dump-hookassembly suspending a body therebelow on a cable extending through saidaligned slots and over said dump-hook assembly; releasable locking meanspositioned within said travelling boom for locking said dump-hookassembly in said stowed position; contact means positioned within saidfixed beam; trigger means operably connected to said locking means toactuate said locking means to alternately release and lock saiddump-hook assembly from and into, respectively, said locking means, andpositioned on said travelling boom (1) so that it contacts said contactmeans on said fixed beam at substantially the same time as said secondstop means on said travelling boom engages said first stop means on saidfixed beam to release said dump-hook assembly for movement along saidtravelling boom toward said first end thereof at substantially the sametime as said travelling boom stops its outward travel relative to saidfixed beam and (2) so that it moves out of contact with said contactmeans at substantially the same time as said dump-hook assemblyre-engages said locking means to lock said dump-hook assembly in saidstowed position; third stop means positioned within said travelling boomfor engagement with said dump-hook assembly when said dump-hook assemblyre-engages said locking means; and fourth stop means positioned withinsaid travelling boom adjacent its first end to limit movement of saiddump-hook assembly toward said first end.
 6. The davit of claim 5wherein: said travelling boom defines a pair of inwardly-facing,opposing guide channels extending from adjacent saiD first end to atleast adjacent said locking means and further defines a cut-out adjacentsaid first end to provide vertical communication of said guide channelswith the exterior of said travelling boom through the top thereof; andsaid dump-hook assembly includes first and second roller meansreceivable by said travelling boom guide channels for guiding saiddump-hook assembly therealong, said first roller means being positionedclosest to said first end of said travelling boom and said second rollermeans being spaced therefrom so that said second roller means rotatesout of said guide channels through said cut-out when said dump-hookassembly engages said fourth stop means and rotates about a transverseaxis through said first roller means under the influence of the weightof said body.
 7. The davit of claim 6 which further includes: firstvalley stop means disposed within said travelling boom adjacent saidfirst end and sized to partially receive said first roller means of saiddump-hook assembly substantially at the same time as said dump-hookassembly engages said fourth stop means adjacent said first end of saidtravelling boom.
 8. The davit of claim 7 which further includes: thirdroller means rotatable carried within said fixed beam adjacent an endthereof through which said travelling boom projects; and second valleystop means disposed under said travelling boom intermediate said firstand second ends to partially receive said third roller means, saidsecond valley stop means being positioned so that said second valleystop means receives said third roller means at substantially the sametime as said trigger means contacts said contact means and said firstand second stop means abut each other.
 9. The davit of claim 6 whereinsaid dump-hook assembly further includes: a pair of spaced platesdefining a pair of aligned, generally horizontal slots which form amouth opening toward said first end of said travelling boom, said firstand said second roller means being rotatably mounted on outwardly-facingsides of said spaced plates; and a sheave rotatably carried by andbetween said first and second plates between said first roller means.10. The gravity davit of claim 5 which further includes: means forsupporting said gravity davit above a deck at an angle relative theretowith said first end of said fixed beam projecting downwardly so thatsaid travelling boom and said dump-hook assembly are free to roll alongsaid fixed beam and said travelling boom, respectively, under theinfluence of gravity; said cable extending through said fixed beam andsaid travelling boom and over said dump-hook assembly to attach at oneend to said body suspended below said dump-hook assembly and at itsother end to a winch; brake means associated with said winch forcontrolling the rate of gravitationally-induced movement of saidtravelling boom and said dump-hook assembly; and power means connectedto said winch for retracting said travelling boom into said fixed beamand for returning said dump-hook assembly to said stowed position.
 11. Atelescoping gravity davit comprising: a hollow fixed beam having aninboard and an outboard end and defining an axially-aligned, elongatedslot extending from said outboard end a substantial distance toward saidinboard end along the bottom of said fixed beam; a hollow, travellingboom sized to telescope into said fixed beam and having an inboard endand an outboard end and defining an axially-aligned, elongated slot inits bottom wall vertically spaced above said elongated slot in saidfixed beam and extending from said outboard end a substantial distancetoward said inboard end, said travelling boom further defining a pair ofinwardly-facing, opposing guide channels extending from said outboardend a substantial distance toward said inboard end, said guide channelscommunicating with the exterior of said travelling boom through acut-out in the top thereof adjacent said outBoard end; first movementmeans carried on said travelling boom; second movement means disposedwithin said fixed beam for cooperation with said first movement means toprovide rolling movement of said travelling boom with respect to saidfixed beam when said fixed beam is tilted with respect to thehorizontal; first stop means disposed within said fixed beam; secondstop means carried on said travelling boom for engagement with saidfirst stop means to limit outboard-directed movement of said travellingboom relative to said fixed beam; a dump-hook assembly disposed withinsaid travelling boom for movement relative thereto between an outboardposition adjacent said outboard end of said travelling boom and aninboard position intermediate said ends of said travelling boom, saidelongated slots and said opposing guide channels extending inboard tosaid inboard position of said dump-hook assembly when said travellingboom is substantially telescoped into said fixed beam, said dump-hookassembly comprising, a pair of vertically-aligned, spaced platesdefining a pair of aligned, generally horizontal slots forming a mouthopening toward said outboard end of said travelling boom, first andsecond roller means rotatably mounted on outwardly-facing sides of saidspaced plates and sized to be received by said guide channels in saidtravelling boom for guiding said dump-hook assembly therealong, saidfirst roller means being positioned closest to said outboard end of saidtravelling boom and said second roller means being spaced therefrom sothat said second roller means rotates out of said guide channels throughsaid cut-out when said dump-hook assembly is rotated about a transverseaxis through said first roller means, and a sheave rotatably carriedbetween said plates between said first roller means for guiding a cablethereover; locking means disposed within said travelling boom forlocking said dump-hook assembly in said inboard position; contact meanspositioned within said fixed beam; trigger means operably connected tosaid locking meand and positioned on said travelling boom (1) so that itcontacts said contact means on said fixed beam at substantially the sametime as said second stop means on said travelling boom engages saidfirst stop means on said fixed beam to release said dump-hook assemblyfrom said locking means for movement along said travelling boom towardsaid outboard end thereof at substantially the same time as saidtravelling boom stops its outboard-directed travel relative to saidfixed beam and (2) so that it moves out of contact with said contactmeans at substantially the same time as said dump-hook assemblyre-engages said locking means; third stop means positioned within saidtravelling boom for engagement with said dump-hook assembly when saiddump-hook assembly re-engages said locking means at its inboard positionto limit inboard-directed movement of said dump-hook assembly; fourthstop means carried within said travelling boom adjacent its saidoutboard end for limiting outboard-directed movement of said dump-hookassembly, said fourth stop means being positioned outboard of saidcut-out a spaced dis-tance to permit rotation of said second rollermeans out of said guide channels when said outboard-directed movement ofsaid dump-hook assembly stops; first valley stop means positioned withinsaid guide channels of said travelling boom adjacent its outboard endand sized to partially receive said first roller means at substantiallythe same time as said dump-hook assembly con-tacts said fourth stopmeans; second valley stop means carried on the underside of saidtravelling boom and engageable with said second movement means atsubstantially the same time as said first and second stop means engageeach other.
 12. The gravity davit of claim 11 wherein: said firstmovement means comprises, a first pulley carried on and extending abovesaid travelling boom adjaceNt its inboard end, a second pulley attachedto and depending from said travelling boom adjacent its inboard end, andtrack means on the undersurface of said travel-ling boom extending fromadjacent its outboard end towards its inboard end; and said secondmovement means comprises, a first rail attachment to and depending fromthe roof of said fixed beam and extending from adjacent its inboard endtowards its outboard end for engagement with said first pulley, a secondrail attached to and extending upwardly from the floor of said fixedbeam and extending from adjacent its inboard end towards its outboardend for engagement with said second pulley, and roller means disposedwithin said fixed beam adjacent its outboard end and extending upwardlyfrom said floor of said fixed beam for engagement with said track meanson said travelling boom, said roller means being partially receivable bysaid second valley stop means.
 13. The gravity davit of claim 11 whichfurther includes: means for supporting said gravity davit above a deckat an angle relative thereto with said outboard end of said travellingboom projecting downwardly so that said travelling boom and saiddump-hook assembly are free to roll along said fixed beam and saidtravelling boom, respectively, under the influence of gravity; saidcable extending through said fixed beam and said travelling boom andover said dump-hook assembly sheave to attach at one end to a bodysuspended below said dump-hook assembly and at its other end to a winch;brake means associated with said winch for controlling the rate ofoutboard-directed movement of said travelling boom and said dump-hookassembly; and power means connected to said winch for drawing saidtravelling boom and said dump-hook assembly inboard.